DOOR AS 1702972 - Caterpillar

Upstroking
Illustration 3 g00577339
Variable Displacement Piston Pump And Compensator Valve (1) Signal line, (2) Flow compensator, (3) Pressure compensator, (4) Pump output, (5) Actuator piston., (6) Cylinder barrel and pistons, (7) Swashplate, (8) Drive shaft, (9) Torque limiter, (10) Spring, (11) Bias spring, (12) Bias piston, (13) Yoke pad, (A) Signal oil, (B) Pressure oil., (C) Return oil, (D) Suction Oil. and (E) Reduced pressure oil.When the pump increases the output due to the demand for the increased flow of oil the pump is upstroking. Because of the increased flow demand, the signal pressure combines with the force of the spring in cavity.This combination of signal pressure and spring force is greater than the pump discharge pressure. This combination of signal pressure and spring force causes the spool to move down. As the spool moves down, the spool blocks the flow of the supply oil to the actuator piston. Oil in the passage for the actuator piston drains into the passage in the pump controller.The oil then flows past the flow compensator spool. The oil then flows past the pressure compensator. The oil then flows through the passage into the case drain.Supply oil flows through a passage to bias piston (12). The oil combines with the force of bias spring (11) and with the spring for the torque limiter. This causes swashplate (7) to upstroke.This increases pump flow. As flow requirements are satisfied the pump output pressure increases. The pressure increases until the pressure in the passage moves the flow compensator spool up to the metering position. Destroking
Illustration 4 g00577345
Variable Displacement Piston Pump And Compensator Valve (1) Signal line, (2) Flow compensator, (3) Pressure compensator, (4) Pump output, (5) Actuator piston, (6) Cylinder barrel and pistons, (7) Swashplate, (8) Drive shaft, (9) Torque limiter, (10) Spring, (11) Bias spring, (12) Bias piston., (13) Yoke pad, (A) Signal oil, (B) Pressure oil, (C) Return oil, (D) Suction Oil and (E) Reduced pressure oil When the pump decreases the output due to the decreasing demand for the flow of oil the pump is destroking. The decreasing demand for the flow of oil causes the signal pressure in the cavity to be less than the pump pressure in the passage. The combination of the signal pressure and the force of the spring is less than the pump pressure in the passage. The spool is pushed up. Oil behind actuator piston (5) cannot flow through the passage to the case drain. Pump oil now flows through the passage, past the spool, through the passage and into the actuator piston (5). Pump pressure behind actuator piston (5) is now greater than the combined force of the bias piston (12) and bias spring (11). The angle of the swashplate (7) decreases. This decreases pump output and system pressure decreases.Once the lower flow requirements are met, the flow compensator spool moves down to the metering position. Swashplate